1. Field of the Invention
This invention relates to cargo carrying containers and, more particularly, to a cargo carrying container with a peripheral wall structure that extends around a cargo storage space and has panels that are reinforced by side post assemblies.
2. Background Art
Over the years, a multitude of designs have been developed for peripheral wall structures on cargo carrying containers, for either single, or multi-model applications. Designers of these cargo carrying containers seek to optimize the volume of the cargo storage space within the constraints imposed by governmental agencies that regulate this industry. This space maximization must not be carried out so as to significantly compromise the integrity of the cargo container. The peripheral wall structures must be designed to withstand vertical, transverse and lateral loading forces that may be encountered in many different environments and under many different conditions.
It is well known to construct a cargo container with a peripheral wall structure between upper and lower rail assemblies to produce a cubicle cargo space. The upper and lower rail assemblies are respectively integrated into roof and floor assemblies and tend to maintain the overall squared shape of the cargo container.
In use, the cargo container is subjected to a number of different static and dynamic forces. The weight of the roof assembly is borne by the peripheral wall structure. In the event that the cargo container is mobilized through a wheeled carriage or provided with a support, as for cooperating with a rail car, loading is imparted through the carriage, a coupler assembly for drawing the cargo container and landing gear aft of the coupler assembly, and through any frame designed for support upon a rail car.
In addition to the aforementioned vertical loads, non-vertical loading forces are imparted to the peripheral wall structure by wind, shifting of cargo, and bending/distortion as the cargo container is transported, be it upon its own carriage or upon a rail car. Additionally, non-vertical forces are imparted by reason of applying anchoring forces through the peripheral wall structure to the cargo within the storage space, to prevent shifting thereof.
It is well known to construct peripheral wall structures with a plurality of flat panels, joined edge-to-edge, or in lapped relationship, to produce a continuous shape. At regularly spaced intervals, including at locations at which the panel edges are butted or lapped, vertically extending, elongate side post assemblies are utilized. Commonly, the side post assemblies are made from steel sheet material that is formed to produce a generally “U” shape defined by a base and spaced, parallel legs. The legs have outturned flanges through which the side post assemblies are secured to one or more panels at strategically selected locations.
The nature of the wall panels, the side post assemblies, and their interaction, dictates the overall strength and integrity of the peripheral wall structure. The depth of the side post assemblies also determines in good part the degree of their rigidity and ability to resist flexing under loading. Generally, the deeper the “U”, the more resistant the side post assemblies are to bending. However, by increasing the depth of the side posts, the cargo space is reduced correspondingly. At the spaced side walls, the loss of volume due to this increase in depth is doubled.
Consequently, it is preferred to make the depth of the “U” as small as possible without adversely compromising integrity. The loss of strength due to the reduced depth can be compensated for to a certain extent by increasing the strength of the material making up the side post assemblies and the panels. While increasing the thickness of the panels and side post assemblies does add strength, it also adds weight to the overall container, which translates into lost revenue by reason of increased loading on the towing equipment and thereby increased fuel consumption.
Thus, the industry had devised numerous different configurations of side post assemblies that potentially allow lighter gauge materials to be used for the side post assemblies and panels. This reduction in material gauge, while desirable from a weight reduction standpoint, introduces additional complications.
For example, the base of the “U” on the side post assemblies commonly serves as a location for discrete logistic slots used for components that effect bracing and allow cargo control by reason of limiting shifting thereof within the storage space. A base that is relatively thin may be prone to failure under forces applied through mechanisms directed through the logistics slots and braced against the base. This balance between weight control and strength for logistics slots has lead designers in many cases to use a gauge of material that is heavier than desired but one that will adequately resist failure in the region around the logistic slots. It may be that in such a case the overall weight of the side post assembly is greater than optimal and the strength of the base in the vicinity of the logistic slots is less than optimal.
The industry continues to seek out new designs of side post assemblies that produce an effective balance between strength, weight control, and maximization of storage space.